The Rev Jesse Jackson insisted that it is "not too late to stop this war" and urged protesters to "march until there is peace and reconciliation".

"War should be necessary as a last resort, and not pre-emptive, and it should have moral authority," he said.

"Today, we can stop this war. It's cold outside, but our hearts are warm. All of you together are generating some serious street heat.

"George Bush can feel it, Tony Blair can feel it: turn up the heat."

He attacked the Bush administration, saying: "America is a great nation: better than the vision of our leadership," and urged Mr Blair to "listen to the voices of the British people".

Ken Livingstone

The Mayor of London, Ken Livingstone, launched a scathing attack on the US president, George Bush, during his address to crowds in London's Hyde Park.

"This is a president who uses the death penalty with complete abandon and disregard for any respect for life. This is no example," Mr Livingstone said.

"So let everyone recognise what has happened here today: that Britain does not support this war for oil. The British people will not tolerate being used to prop up the most corrupt and racist American administration in over 80 years.

"If you listened to Tony Blair today ... he talked about giving more time to the inspectors, he talked about the need for a new UN resolution, and there's the weakness.

"There are nations on the security council that are for sale. Nations who will be offered the liquidation of their debts and offered major grants. Let's watch the security council like hawks.

"Let's not, having won the moral case and demonstrated the opposition of the world, lose this fight because of corruption and vote-buying on the security council."

Tony Benn

Labour MP Tony Benn said that anti-war protesters had "formed a new political movement" which would last beyond the Iraq crisis.

"It's to stop a war in Iraq but it must be about other matters as well," he said.

"It must be about the establishment of a Palestinian state. It must be about democracy in the Middle East - there is no democracy in Saudi Arabia or Iraq - and about some democracy in Britain as well, and letting parliament decide. "We are starting something really big, and our first task is peace in Iraq: but we must not stop until we have achieved the objectives which have brought us to Hyde Park this afternoon."

Charles Kennedy

The Liberal Democrat leader, Charles Kennedy, told the crowd that he was "not persuaded" by the case for war in Iraq.

"The arguments have been contradictory and inconsistent," Mr Kennedy said. "The information has all too often been misleading as well as inconclusive. It's no wonder people are scared and concerned.

"Given the evidence we heard yesterday in New York from Dr Blix, there can be, as we stand, no just or moral case for war against Iraq.

"If we reach the stage, at some point in the future, where British troops are asked to enter some form of military conflict, that's got to be achieved in a democratic way.

"The House of Commons should be given the right it so far has been denied: the right of a vote on whether it believes our forces should be sent into battle.

He called on the prime minister to recall the commons when it is in recess next week and "make a full statement", and branded the Iraq crisis "the riskiest moment for Britain since Suez".

Mo Mowlam

Former Labour minister Mo Mowlam told the crowd that Mr Blair and the government had themselves in "a right corner" over Iraq.

"Things can only get better if we stick together," she added. "Keep it peaceful. Because being peaceful, people will have no excuse not to listen.

"There is a position now ... that if a country has a lot of people killed from poverty and military dictatorship, if that number is smaller than that killed by war then the war is OK. That, to me, is totally illogical."

Harold Pinter

The playwright Harold Pinter described the US as "a country run by a bunch of criminals ... with Tony Blair as a hired Christian thug".

"The planned attack on Iraq is a pre-meditated attack of mass murder," he added. "Resistance is embodied today in this massive gathering, and the word I want to direct to Tony Blair is resign, resign, resign."

Bianca Jagger

Bianca Jagger accused the prime minister of "listening to President Bush rather than the voices of the British people".

"We want to live in a world where peace, democracy and security are enshrined in the UN charter," she added.

"I would like to see democracy in Iraq, but not by carpet bombing Iraq and killing innocent civilians."